take this for what it's worth, which ain't much...........
my wife's 94 concorde, which is a front drive, the converter liked to hunt between lock up and unlock at a steady 2000rpm.
i don't know where i heard or read about this, but i dumped in a bottle of rear gear clutch additive. i think it was the yukon brand stuff, but i'm not sure.
anyway, the converter lock/unlock/shudder, whatever it was, was gone the first drive, and hasn't returned in over three years.
just my experience in life. your mileage will vary.